Not seen before. The JIC reference gives it some kudos. However it requires the exclusion of molluscs from the enclosed area, if you knew that was possible, it requires replacement after rainfall, and a considerable volume to produce the barrier dimension given. Harmful?, not , effective as described, maybe but an economic proposition? Not for my requirement. Often its the small keel type slugs that are the biggest hazard, the 6" rovers can be skewered!!
The link shows that the "Gardensuperstore"(sic) are "out of stock" so somebody has tried it? I await reports.